QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 660 LOW NOISE MICROPOWER LINEAR VOLTAGE REGULATOR LTC1844 DESCRIPTION Demonstration circuit DC660 is a low noise micro- small size ceramic capacitors, tiny SOT-23 package of power voltage regulator using the LTC1844 ultra-low the LTC1844, plus its low quiescent current dropout CMOS linear regulator, which comes in a tiny maximum 80uA over temperature, the DC660 voltage 5-Pin SOT-23 package. The DC660 has an input volt- regulator is ideally suited for hand-held applications, age range from 1.8V to 6.5V, and is capable of deliv- such as cellular phones or PDAs. ering 150 mA max. The DC660 is able to use ceramic Gerber files for this circuit are available. Call the capacitors, due to the LTC1844 capability of maintain- LTC Factory. ing stability with ultra-low ESR capacitors. With the QUICK START PROCEDURE DC660 is easy to set up for evaluating the perform- power, and, just as in the 1.5V test, the out- ance of the LTC1844. For proper measurement put voltage should read Vout +/- 2% toler- equipment configuration, set up the circuit accord- ance under static line and load conditions, ing to the diagram in Figure 1. and +/- 4% tolerance under dynamic line and load conditions. Please follow the procedure outlined below for 5. When finished evaluating, turn off the input proper operation. power. 1. Before proceeding to test, insert jumper JP1 into the 1.5V option and apply no load across Vout. Warning - If long leads are used to power the demo circuit, the input voltage at the part could ring. 2. Apply 1.6V across Vin (to Gnd). Draw This ringing could affect the operation of the circuit 10mA of load current. Measure Vout it or even exceed the maximum voltage rating of the should be 1.5V +/- 2% (1.47V to 1.53V). IC. To eliminate this, insert a small tantalum ca- 3. Vary the input voltage from 1.6V to 6.5V pacitor (for instance, an AVX part and the load current from 10 mA to 100 mA. TAJW226M010R) on the pads between the input Vout should measure 1.5V +/- 4% (1.44V to power and return terminals on the bottom of the 1.56V). demo board. The (greater) ESR of the tantalum will 4. Turn off the input power and move jumper dampen the (possible) ringing voltage due to the JP1 into any of the remaining output voltage use of long input leads. On a normal, typical PCB, options: 1.8V, 2.5V, 2.8V, or 3.3V. Re-apply with short traces, the capacitor is not needed. 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 660 LOW NOISE MICROPOWER LINEAR VOLTAGE REGULATOR Figure 1. Proper Measurement Equipment Setup Figure 2. Measuring Input or Output Ripple 2